SOURCEFORGE » RALF » 2015 SDR for rapid prototyping of radio communications

h1. *6. Results*

When the communication between the USRPs was established, the transmitted constellation below was obtained.

p=. !{width: 30%}https://sourceforge.isae.fr/attachments/download/1513/Tx_Constellation.png(Transmitted Constellation)!

_Figure 6.1 Transmitted Constellation_

Using an IQ sampling of $500k$, obtaining a symbol rate of $62500$ symbols/sec, without any noise, the received constellation is shown below. The $BER$ in this case is, evidently, 0.

p=. !{width: 30%}https://sourceforge.isae.fr/attachments/download/1511/Rx_Constellation_no_noise.png(Received Constellation)!

_Figure 6.2 Received Constellation without AWGN_

The constellation on Figure 6.3 was obtained when adding AWGN, for a target $E_b/N_0$ (received $E_b/N_0$) of 5.The constellation will vary as the values of $E_b/N_0$ vary, making it either noisier, or making it resemble a noiseless channel.

p=. !{width: 30%}https://sourceforge.isae.fr/attachments/download/1512/Rx%20_Constellation_AWGN.png(Noisy Constellation)!

_Figure 6.3 Noisy Constellation_

With AWGN, the $BER$ is calculated, then compared to the theoretical one, obtaining a $BER$ vs $E_b/N_0$ graph like the one depicted below in Figure 6.4. It can be seen that the simulated $BER$ follows, as expected, the same behavior as the theoretical $BER$.

p=. !{width: 60%}https://sourceforge.isae.fr/attachments/download/1514/BERtheory.jpg(Theroretical an Simulated)!

_Figure 6.4 BER vs Eb/No without coding_

The $BER$ is also calculated for a the BCH code or a rate of (roughly) 1/2, and compared to the simulated $BER$ without coding. It can be observed from the graph below, that BCH greatly improves the $BER$. In this case, there is a gain of $3dB$ for a $BER=10^-5$

p=. !{width: 60%}https://sourceforge.isae.fr/attachments/download/1516/BERbch.jpg(BCH Coding)!

_Figure 6.5 BER vs Eb/No with BCH coding_